Installations have been provided for producing cement clinker from cement raw meal which have a rotary kiln and a cyclone suspension heat exchanger with calciner connected upstream of said rotary kiln in the sense of material flow. In the cyclone suspension heat exchanger system, the cement raw meal is preheated by combined cocurrent/countercurrent flow of the hot off-gas of the calcination stage or of the rotary kiln, and the stock material precalcined in the calcination stage is separated from the hot gas in the lowermost cyclone of the cyclone suspension heat exchanger system and fed to the rotary kiln. It is understood that the hot-gas cyclones of the cyclone suspension heat exchanger train, in particular the lowermost cyclone, which comes into contact with hot gas and hot meal at a temperature of for example 700 to 950° C., are subjected to severe mechanical, chemical and thermal loading and thus to severe thermochemical and abrasive wear. This applies in particular to the dip tube intruding into the cyclone separator centrally from above.
In the case of a cyclone separator subjected to these severe loadings it is therefore already known to assemble the dip tube from a plurality of segments and to connect the segments to one another detachably so that, in case of wear, the individual dip-tube segments can be replaced at a relatively low cost in time and labor. The beforementioned prior art features are disclosed in German patent number DE 3228902 C2 issued Feb. 9, 1994 to H. Hercheubach et al for a Cyclone Separator and in German patent number DE 19825206 A1 issued Dec. 9, 1999 to R. Filges et al for a Cyclone Separator. The tops of the dip-tube segments were fashioned in angle shape or hook shape and were suspended from the cyclone cap with the hooks. The hook suspension secured the dip-tube segments against falling downwardly into the cyclone separator in case the radially arranged bolts by which the tops of the topmost row of dip-tube segments are clamped against the cap should come loose as a consequence of wear during the operation of the cyclone separator. From a fabrication standpoint, however, it is costly to form hook-shaped or angle-shaped formed bodies to the dip-tube segment sheets, which are smooth per se, by metalworking and/or welding. There are limits to the casting of metal dip-tube segments in that dip-tube segments, if they are no thicker than approximately 15 mm, can be cast free of inhomogeneities only up to a length of approximately 120 cm. Large hot-gas cyclones, however, require correspondingly large dip tubes in which the individual segments are far more than 120 cm long, and must not be too heavy for reasons of installation. The service life of dip-tube segments in known hot-gas cyclones is furthermore shortened if the lower ends of the dip-tube segments, which intrude freely into the interior of the hot-gas cyclone and are subjected to especially abrasive attack by the impinging hot gas/solids suspension, are not specially protected.